no, it is not new. It is just that many businesses do not know how to deal with marriage extensions, as then they can't hold the visa extension as a threat if you don't work.
Anonymous participant if you have been seeing the same medical doctors for your conditions then they should have no problem providing you with the needed letters under the soft power option. You are a legitimate reason under medical treatment option.
you are correct in that the homeowner/landlord must file a TM30 on each person staying there within 24 hours, but there is nothing saying they must give you a copy for free. Under bt50 could be reasonable, but not bt500.
understand that it makes no difference if you buy a tourist visa, or enter again on a visa exempt entry. Immigration doesn't care. Don't waste money buying a tourist visa. Just because you bought a tourist visa does not mean Thailand will let you in. Many people over the years found this out the hard way when Thailand immigration determined they were trying to stay long term as a tourist. You've been away long enough that they will let you in, but most likely with your history they will want to see a legitimate return airline ticket, and not a fake one you bought online, as they are fully aware of them. The only problem those on ED visas face is if they do not have the required extensions every 90 days. Again, you'll be let in, just make sure you have required funds, and a return plane ticket. If you can't meet the financial requirements of the DTV, then you won't meet the financial requirements of any other non-immigrant visa extension. Like I said at the beginning don't waste your money buying single entry tourist visa as it will make no difference. If you want to buy a tourist visa then get the multi-entry tourist visa, the METV. With it you can stay almost 9 full months, with just two border bounces, and 30 day extensions.